Circuit breaker



Oct. 28, 1947. o. 5. JENNINGS CIRCUIT BREAKER 0 4 9 1 5 l V. 1 H J d e li F 4 Sheets-Sheet l INVENTOR 'OZI'UIPI'gYclWfiiWS a B Z moan:

WITNESSES: 'JW

Oct. 28, 1947. o. 5. JENNINGS 2,429,722

0 IRCU IT BREAKER 4 Sheets-Sheet 2 Filed July 115, 1940 wmursszs: 77 198M JNVENTOR Oliverfidzwkys.

- Oct. 28, 1947. o. 5. JENNINGS 2,429,722

CIRCUIT BREAKER Filed July 13, 19 40 4 Sheets-Sheet 3 M .1 If Y k; "I aQ WITNESSES: INVENTOR 47% Olive/- 5. v/yyjys I MWM Oct. 28, 1947. o. 5.JENNINGS CIRCUIT BREAKER Filed July 13, 1940 4 Sheets-Sheet 4 i lllINVENTOR dive/ 5. Jsllll fys \H h m d r w m 7/4/7 nW NM. WNW

Patented Oct. 28, 1947 CIRCUIT BREAKER Oliver S. Jennings, Pittsburgh,Pa., asslgnor to Westinghouse Electric Corporation, East Pittsburgh,Pa., a corporation of Pennsylvania Application July 13, 1940, Serial No.345,264

25 Claims. 1

The invention relates to circuit interrupters, and more particularly tomanually and automatically operable low voltage circuit breakers forcontrolling lighting and other small and moderate power electriccircuits;

An object of the invention is the provision of an improved circuitbreaker of the class described which is compact and light in weight,accurate and reliable in operation, and inexpensive to manufacture.

Another object of the invention is the provision of an improved circuitbreaker in which all parts thereof are removably mounted in a novelmanner in a two-part separable enclosing housing of insulating materialwithout the use of any frame other than the enclosure and withatingmechanism and separate trip device, both supported in recesses andsurfaces provided in a two-part housing of molded insulating materialwith the parts and surfaces disposed so that the reactions on the partscause'them to naturally seat against fixed surfaces in such a manner asto insure substantially constant performance and accuracy of operationdespite the degree of looseness of fit of the parts in the housing.

Another object of the invention is the provision of a circuit breakerembodying an opensided casing having recesses and surfaces for receivingand supporting the contact means and operating means and havingadditional recesses and surfaces for receiving and supporting either acombined magnetically and thermally responsive trip device, or athermally responsive trip device, or a magnetically responsive tripdevice, the parts being removably mounted through the open side of thecasing and retained in mounted position by a second casing memberremovably mounted on the open side of the casing, without any of theparts being positively fastened to the casing sections.

Another object of the invention is the provision of a. circuit breakerembodying an improved thermally and magnetically responsive trip de- 2vice in which the thermally responsive bimetal trip element normallyopposes tripping or release of the breaker mechanism, the constructionof the trip device being such that bimetal trip elements of differentstiffness or thickness may be substituted without affecting theoperation of the electromagnetic trip means.

Another object of the invention is the provision of a thermally andmagnetically controlled circuit breaker which provides a greater timedelay action for a predetermined range of heavy overloads than isobtainable by conventional circuit breaker constructions.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to structure and operation together withadditional objects and advantages thereof will be best understood fromthe following detailed description of several embodiments thereof whenread in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevational view, partly in section, of a circuitbreaker constructed in accordance with the invention, one section of thetwo-part insulating housing having been removed to more clearlyillustrate the invention, the breaker mechanism parts being shown in thecircuit closed position;

Fig. 2 is a transverse sectional view of the complete breaker takensubstantially along the line 11-11 of Fig. 1 and looking in thedirection of the arrows;

Fig. 3 is a side elevational view of the breaker, similar to Fig. 1,showing the position of the parts an instant after tripping of thebreaker;

Fig. 4 is a transverse sectional view of the complete breaker takensubstantially along the line IV-IV of Fig. 3 and looking in thedirection of the arrows;

Fig. 5 is a side elevational view of one part of the two-part moldedinsulating housing of the breaker;

Fig. 6 is a side elevational view of the removable side part of thehousing showing the interior side thereof;

Fig. 7 is a fragmentary view of the circuit breaker with the sidesection of the housing removed showing a modified form of trip device;

Fig. 8 is a fragmentary view of the circuit breaker with the side of thehousing section removed showing a thermally responsive trip device inmounted position in the casing in place of the combined magnetically andthermally responsive trip device shown in Fig. 1;

of the arrows, both sections of the housing being shown; and

Fig. 11 is a fragmentary sectional view of the breaker takensubstantially on the line Xi-XI of Fig. 1 and looking in the directionof the arrows, both sections 01' the housing being shown.

My prior Patent 2,190,517, issued February 13, 1940, and assigned to theassignee of the present invention discloses a thermal circuit breaker inwhich the movable parts are removably supported on pivot pins in atwo-part separable insulating casing. The present invention isdistinguished from the aforesaid patent in a number of respectsincluding the following: The present invention provides an improvedcircuit breaker operating mechanism and improved trip device which areseparately mounted in recesses and surfaces provided in the two-partinsulating casing with the parts and surfaces disposed so that thereactions on the parts cause them to naturally seat against fixedsurfaces in such a way as to insure substantially constant performanceand accuracy of operation of the breaker despite the degree of loosenessof fit of the parts in the housing. The recesses and surfaces of thehousing are arranged to receive and support either a combined magneticand thermal trip device, or a thermal trip device, or a magnetic tripdevice, for use with the same mechanism. All parts including theterminals are removably supported without being positively fastened tothe housing. In my Patent 2,190,517 only a single type of bimetal tripelement can be used and this element is carried by the movable contactarm, and the terminals are positively fastened to the housing by screwfastenings.

In accordance with another of its phases, the present inventionconstitutes a further development of the invention disclosed and claimedin my copending application Serial No. 339,466, flied June 8, 1940, nowPatent 2,329,053, issued September 7, 1943, and assigned to the assigneeof the present invention. One embodiment of the trip device of thepresent invention is generally similar to that disclosed in theaforesaid copending application but is distinguished therefrom by theprovision of a resilient means between the bimetal element and the latchwhereby the operation of the electromagnetic trip means is independentof the thickness or stiffness of the bimetal element so that bimetalelements of different thickness or stiffness may be substituted withoutaffecting the operation of the electromagnetic trip means. Anotherdistinguishing feature of the present invention over the aforesaidcopending application with reference to one form of the trip device isin the provision of a double armature with the armature sectionsseparated by a low resistance conducting member whereby a greater timedelay action is obtained in a predetermined range of overload currents.

Referring to Figs. 1-6 of the drawings, the circult breaker comprises ingeneral a twopart separable housing |5 of molded insulating material, astationary contact IT, a cooperating movable contact 9 carried by aswitch arm 2|, an operating mechanism indicated generally at 23, acurrent responsive trip device indicated generally at 25 and a pair ofterminals 21 and 29 for connecting the breaker in an electrical circuit.

The housing H5 is adapted to enclose all of the parts of the circuitbreaker mechanism other than the operating end of the manually operableoperating lever and the terminal ends of the terminals, and the housingcomprises two separable sections or parts 3| and 33 having the divisionplane or Joint between them disposed substantially parallel to the planeof movement of the switch arm 2|. The housing sections 3| and 33 serveas the frame for the breaker and are molded to provide various recessesand surfaces for removably receiving and supporting all of the parts, aswill be hereinafter described, whereby the parts are slidably receivedthrough the open side of the housing section 3| when the sections areseparated and are retained in mounted position when the housing sectionsare assembled, without any of the parts being positively fastened to thehousing.

The housing section 3| has one solid side wall 35, end walls 31 and 39,a bottom wall 4|, and a front wall 43 (Figs. 1 and 5). The front wall 43is provided with an elongated notch 45 and well 41 both open at the openside of the housing section for accommodating the operating end andhandle of the manual operating lever of the breaker. The front wall 43of the housing section 3| is also provided with a pair of projections 49and 5| for limiting movement of the operating lever, and each projectionis provided with a slot 53 for receiving and fitting the ends of anarcuate closure projection formed on the inner surface of the otherhousing section 33. The bottom wall 4| of the housing section 3| has anopening 55 formed therein adjacent the stationary and movable contactsof the breaker for venting the arc gases and this opening is bounded bya slot 51 on three sides thereof, the opening 55 and slot 51 being openat the open side of the housing section 3|. The slot 5'! is adapted toslidably receive and support a bottom baffle plate of an arcextinguisher which will be hereinafter described.

The opposite ends of the housing section 3| are formed to provide niches59 and Bi which are open at the end, front, and open side of the housingsection 3| for providing access to the terminal ends of the terminals2'! and 29 of the breaker. The upper end wall 31 of the housing sectionis provided with a recess 63 open at the front and open side of thehousing section for accommodating a terminal screw 65 which is threadedin an opening in the terminal end of the upper terminal 27 to provide ameans for connecting this terminal of the breaker to an electricalcircuit. An angle shaped transverse slot 9! is formed in the upper endwall 31 of the housing section 3i and this slot opens at its upper endinto the niche 59 and at its lower end into the main chamber of thehousing section 3|. The slot 61 is open at the open side of the housingsection for slidably receiving the upper terminal 21, the walls of theslot serving to support the terminal 21 in mounted position.

The lower end wall 39 of the housing section 3| is formed to provide arecess H which is open at the front and open side of the housing section3| for accommodating a terminal screw 13 which is threaded in an openingprovided in the lower terminal 29 for connecting this terminal to anelectrical circuit. The recess opens at 12 (Fig. 5) into a chamber 15formed in the lower end of the housing section 3| for accommodating anelectromagnetic trip means which will be hereinafter described.

The housing section 33 forms a closure for the open side of the housingsection 3I and is formed as a generally flat plate having recesses andpro- Jections on its inner surface for aiding in supporting certainparts of the circuit breaker. The housing sections 3i and 33 are adaptedto be secured together in assembled relation by three bolts 11 (Fig. 2)which extend through aligned openings 18 (Figs. 2. and 6) providedtherefor adjacent three corners of each housing section. The heads ofthe bolts are adapted to seat in counter-sunk holes in the housingsection 3I and the ends of the bolts are threaded to engage nuts 8I(Fig. 2) disposed in counter-sunk holes provided therefor in the outersurface of the closure section 33.

The upper terminal 21 comprises a flat strip of conducting material bentat right angles at several points so that it has a step shape, and thestationary contact I1 is rigidly secured to the lower end of thisterminal. The lower terminal 28 comprises a substantially rectangularflat plate of conducting material having an ear 83 on one side which isbent at a right angleto the terminal. The other side of the terminal 28has a projection 88 formed integral therewith (Figs. 4 and which-isadapted to fit snugly in a rectangular recess 81 (Fig. 5) providedtherefor in the wall 38 of the housing section 3I. The cover section 33of the housing is provided with a rectangular recess 88 (Figs. 6 and 10)which fits the ear 83 of the terminal 28 when the casing sections areassembled to securely retain the terminal in mounted position. The lowerwall 38 of the housing section 3| is also provided with a slot 8| (Figs.1 and 5) into which the upper edge of the terminal 28 projects as seenin Figs. 1 and 10.

The terminal 21 is removably inserted in the housing section 3I bysliding the terminal edgewise into its slot 81 through the open side,and is securely retained in mounted position when the cover section 33of the housing is secured in assembled position on the housing section3I. Similarly, the lower terminal 28 is inserted in the recesses andslots provided therefor in the lower end of the housing section 3|, andis securely retained in mounted position by the cover section 33 of thehousing-when the housing sec-- tions are assembled.

The are extinguishing device comprises a pair or U-shaped elements 83(Figs. 1 and 2) of magnetic material which are assembled between sideplates 88 of arc resistant insulating material. The side wall 38 of thehousing section H is provided with a pair of rectangular recesses 81(Fig. 5) which are adapted to receive and fit one end of the U-shapedmagnetic elements 83 when the arc extinguishing device is assembled inthe housing. The legs ofthe U-shaped magnetic elements 83 and theinsulating side plates 38 are disposed on opposite sides of the path ofmovement of the movable contact I8. A baffle plate 88 is removablymounted in the slot 81 provided in the housing section 3I. by slidingthe plate edgewise into the slot 81. The plate 88 engages the back edgesof the insulating side plates 88 and thus aids in supporting the sideplates, and the baffle plate 88 is provided with a plurality of openingsI8I to allow the escape of the arc gases through the back of thehousing. A plate I83 of arc resisting insulating material is removablymounted in an L-shaped slot I88 (Fig. 5) provided in the upper end wall31 and side wall 38 of the housing section 3I for projecting theoperating mechanism from the arc. The plate I83 is removably inserted inthe housing section 3I by sliding the same edgewise into the slot I88and is retained in mounted position by the cover section 33 of thehousing. Another plate I81 of are resistant insulating material isremovably mounted in an L-shaped slot I88 (Fig. 5) formed in the upperend wall 31 and the side wall 38 of the housing section 3 I. The plateI81 is disposed immediately above the arc extinguisher and serves toprotect this portion or the housing from damage by the are as the arc ismoved by the magnetic elements 83 towards the bottom wall of thehousing. The insulating side plates 88 of the arc extinguisher areretained in mounted position when the housing sections are assembled byreason of the fact that they are held between the side walls of thehousing I8 and the legs of the U-shaped magnetic elements 83. The upperright-hand corners of the insulating side plates 88 bear against theplate I83 and the edges of the plates parallel to the bottom wall of thehousing bear against the baffle plate 88, so that the plates aresecurely retained in proper position within the housing. The areextinguishing structure and the plates I81 and I83 are removably mountedin the housing section 3| by sliding the same into the recesses andslots provided, therefor through the open side of the housing section3i. The cover sction 33 of the housing is provided with a slot III whichfits the side edge of the baffle plate 88.

The operating means of the circuit breaker comprises a releasablesupporting member I I3 for pivotally supporting the switch arm 2|, amanually operable operating lever I I8, and an overcenter spring II1connected in tension between the switch arm 2I and a part of theoperating lever The releasable supporting member II3'comprises ayoke-shaped lever or cradle having spaced legs II8 (Fig. 2) which areJoined at their upper ends by a cross piece I28 and at their lower endsby a latch element I2I which cooperates with a movable latch of the tripdevice. The cross piece I 28 is formed integral with the spaced legs II8of the releasable member, and the latch element I2I is secured betweenthe lower ends of the legs of the lever by means of retaining pins orrivets I23. The legs of the releasable member II3 are generally V-shapedin side elevation and the switch arm 2I is pivotally engaged at one endin the apex of the releasable member II3. The switch arm 2I isbifurcated at one end to form spaced legs I 28 and the ends oi the legsare notched as indicated at I21 in Fig. 2 for pivotally engaging thelegs of the releasable member I I3 at the apex thereof, as shown inFigs. 1 and 2. The releasable member II3 is mounted for pivotal movementby a pivot pin I28, the ends of which are supported in cylindricalbearing recesses I3I and I33 (Figs. 2, 5 and 6) provided therefor in thehousing sections 3I and 33, respectively, whereby the releasable memberis removably mounted in the insulating housing. The releasable memberII3 is always biased in a counterclockwise direction about its pivot I28as viewed in Fig. 1 by the overcenter spring H1, and is adapted to berestrained in the normal position shown in Fig. i by the latch of thetrip device which engages the latch element I2I of the releasablemember.

The manually operable operating lever H5 is disposed for pivotalmovement within the housing in a shallow V-shaped recess I35 formed inthe side wall 35 of the housing section 3|. The operating lever isrounded at its inner end and this end is pivotally supported in therounded bottom of the V-shaped recess I35 as best shown in Fig. 2. Theouter end of the operating lever H is offset and the offset portionextends out through the notch 45 of the housing section 3| and isprovided with an operating handle I31 which is rigidly secured to theouter oflset end of the lever. The cover section 33 of the housing isprovided with an arcuate projection I28 having an arcuate portion I30which is adapted to underlie the side edge of the notch 45 of thehousing section 3i and cooperate therewith to form a closure for thehandle opening when the housing sections are assembled as shown in Fig.2. The overlap relation between the portion I30 and the side edge of thearcuate portion 45 provides a tortuous path to minimize the danger offlame and hot gases escaping through the handle opening. A stud I39 isrigidly secured to the operating lever II5 adjacent the ofiset outer endthereof and this stud projects laterally from the lever and carries aroller MI at its free end. The cover section 33 of the housing isprovided with an arcuate slot I43 (Figs. 2 and 6) disposed concentricwith the pivot axis of the operating lever for receiving the roller MI.The roller MI bears against the bearing surface formed by the bottomwall I45 of the arcuate slot 143. The roller is adapted to be moved backand forth along the bearing surface I 45 as the operating lever H5 ismoved back and forth between open and closed circuit position. It willthus be seen that the operating lever is pivotally supported in twospaced bearings one comprising the rounded inner end of the V-shapedrecess I35 of the housing section 3! and the other comprising thearcuate bearing surface I45 formed in the cover section 33 of thehousing.

The overcenter spring H1 is disposed between the legs I25 of thebifurcated end of the switch arm 2| and has one end connected to theswitch arm 2i by being hooked into an opening I41 provided in the switcharm. The other end of the overcenter spring is anchored in a notch I49provided in the stud I39 midway between the ends of the stud. The springII1 serves to retain the switch arm 2i in pivotal engagement with the suporting member H3, and the operating lever I I5 in pivotal engagementwith the bearings. The pivot bearings of the pivoted operating lever H5and the pivotedswitch arm 2I and the pivoted support member I I3 arespaced on opposite sides of the overcenter spring II1 as shown in Fig.2, thereby providing a. well balanced construction and insuring smoothand accurate operation oi the mechanism.

The operating lever I I5 is moved in an upward direction to effectclosing of the circuit breaker. As soon as the line of action of theovercenter spring H1 is moved above the pivot axis of the switch arm 2|,the spring acts to move the switch arm N to closed circuit position witha snap action. The operating lever II 5 is moved in a downward directionto open the circuit breaker and as soon as the line of action of theovercenter spring I I1 passes below the pivot axis of the switch arm 2I, the switch arm is thereby caused to move to open circuit positionwith a snap action. The circuit breaker is adapted to be automaticallyopened in response to overload conditions by the trip device 25 whichwill be hereinafter described. The operation of the trip device inresponse to an overload effects release or the releasable supportingmember H3, and the overcenter spring II1 moves the supporting member ina clockwise direction or upward direction about its pivot axis I29thereby shifting the pivot axis of the switch arm 2I above the line ofaction of the overcenter spring H1 and thus causing movement of theswitch arm 2i to an open circuit position with a snap actionirrespective of the position of the operating lever H5. Before thebreaker can be manually reclosed following a tripping operation. it isnecessary to reset the releasable supporting member II3 to its normallatched position. The mechanism is reset following a tripping operationby manually moving the operating lever I I5 downwardly to open circuitposition. The operating lever is provided with a resetting projectionII6 (Fig. 1) which projects laterally from the lever and is adapted toengage and move the releasable member H3 in a clockwise direction ordownward direction back to its normal latched position ,upon downwardmovement of the operating lever H5 to open position. The breaker may bemanually closed following resetting in the manner previously describedfor the closing operation.

The U-shaped magnetic elements 93 of the are extinguisher set up amagnetic field upon opening of the circuit which acts to elongate andmove the arc toward the bai'fle plate IIII, and the arc is quicklyextinguished by the cooling and deionization of the arc gases in a wellknown manner and by the attenuation of the arc.

The trip device 25 is removably mounted in the lower portion of thehousing section II without any part thereof being positively fastened toeither of the housing sections. The trip device comprises, in general, apivoted latch lever I5I controlled by an eiectromagnet I53 and by a.thermally responsive bimetal element I55. The electromagnet comprises aU-shaped core I51 of magnetic material, and a double armature comprisingtwo armature-sections I59 and lil of magnetic material secured to theopposite sides of the pivoted latch lever I5I, and an energizing windingI63 which is wound upon the long leg of the core I51.

The latch lever I5I is preferably formed of a single piece of lowresistance conducting material such as copper and has a yoke-shapedportion providing spaced legs which straddle and are pivoted to thelonger leg of the magnet core I51 by means of a pivot pin I95, as shownin Figs. 1 and 11. The latch lever has a latch element or projection I61struck out therefrom which is adapted to engage the latch element I2I ofthe releasable member II3 to normally hold the releasable member inoperative position. The latching surfaces of the latch elements III andI61 are preferably disposed perpendicular to a line projected from theirpoint of engagement to the center of the pivot pin I65 so that theovercenter spring II1 of the breaker mechanism does not bias the latchlever I5I in either direction.

A tension spring I69 is anchored at one end to a-projection ill of thelatch lever I5I, the coils of the other end of the spring engage thethreads of an adjusting screw I13 whereby the pull of the spring may beadjusted to thereby vary the trip characteristic of the device. Thespring I 59 acts to bias the latch lever I5I to the unlatched orreleased position and the strength of the spring is preferably more thansufficient to overcome the latch load and release the supporting leverII 3 except when the member is restrained by the bimetal element. Thelower end of the biasing spring I39 projects laterally into a verticalslot I10 provided in the side wall 35 of the housing section 3I so thatthe spring is prevented from turning with the screw I13. The lower endwall 39 of the housing section 3| is provided with an opening I13opposite the head of the screw I13 to permit adjustment of the screwfrom outside the housing. I

The thermally responsive bimetal element I55 comprises a flat strip ofbimetallic material bent in a U shape and secured at one end to abracket I15 of conducting material. The bimetal element is mounted inthe housing so that it is free and engages the underside of the free endof the latch lever I and is insulated therefrom by an insulating buttonI11 secured to the free end of the latch lever I5I.

The bimetal element I55 normally assumes a position shown in Fig. 1 andacts to oppose movement of the latch lever to the unlatched position andnormally restrains the latch lever in latching position. When thebimetal element is heated a predetermined amount, it is free and flexesor is moved in a downward direction, that is, away from the operatingmechanism to permit movement of the latch lever I5I toward the unlatchedposition.

The energizing winding I33 of the electromagnet and the bimetal elementI55 are electrically connected in series with the contacts I1 and I3 ofthe circuit breaker so as to be traversed by the current flowing in thecircuit controlled by the breaker. The free end of the bimetal elementis electrically connected to the pivoted supporting member II3 by aflexible shunted conductor I13. The pivoted supporting member H3 and theswitch arm 2| are of conducting material and being in'engagement effectelectrical connection of the movable contact I9 to the flexible shuntconductor I19.

One end of the energizing winding I33 of the electromagnet is brazed tothe ear 33 of the lower terminal 29, and the other end of the windingI33 is brazed to the bracket I15 of the bimetal element I55. Theelectrical circuit through the breaker extends from the upper terminal21 through the stationary contact I1, the movable contact I3, switch arm2|, pivoted supporting lever I I3, flexible shunt conductor I19, bimetalelement I 55, and energizing winding I33 to the lower terminal 29.

The energizing winding I63 of the electromagnet is relatively still sothat it acts to support the bimetal element I55 and the terminal 29 inapproximately correct position for insertion in the housing and so thatthe electromagnet I53,

the bimetal element I55 and the terminal 23 are, in effect, a unit,although the bimetal element and the terminal may be moved relative tothe electromagnet by bending the ends of the energizing winding I63.

The unit comprising the electromagnet I53, the bimetal element I55 andthe terminal 29 is fitted in the housing section 3| by sliding the samesidewise through the open side of the casing in suitable recessesprovided for the unit. The electromagnet is adapted to be disposed inthe chamber 15 of the housing section 3I The long leg of the magnet coreI51 is engaged by surfaces I3I, I33, I85 and I81 of the bottom wall ofthe housing section 3I and the short leg of the magnet core is engagedby the surface 10 I33 formed in the lower end wall 33 of the housingsection and also by a surface I3I of a proiection I33 formed in thehousing section 3|. One side of the magnet core I51 is engaged by thesurface I33 (Figs. 4 and 5) or the housing section 3I, and the otherside of the magnet core is engaged by projections I30 and I92 (Fig. 6)

formed on the inner surface of the cover section 33 of the housing whenthe housing sections are assembled thereby preventing sidewisedisplacement of the electromagnet in the housing. The ends of the pivotpin I35 fit in cylindrical bearing recesses I35 and I31 (Figs. 4, 5 and6) formed in the housing sections 3| and 33, respectively. The housingsections 3I and 33 are each provided with complementary dished recessesI33 and I33 for accommodating the sides of the energizing winding I33.

The bracket I15 of the bimetal element I fits in a slot 2M (Figs. 2, 5and 10) provided in the side wall 35 of the housing section 3I, and oneside of the bracket is bent at right angles, as indicated at 203, andthis bent side fits in a recess 235 (Fig. 5) provided therefor in theside surface of the lower end wall 39 of the housing section H. Thesurface of the bracket I15 which faces the operating means is engaged bythe upper wall of the slot MI and by the surface 231 of the projectionI93 formed in the housing section 3I and the opposite surface of thebracket is engaged by the other wall of the slot 20L From the foregoingit will be seen that the stationary core I51 of the electromagnet I53and the bracket I15 to which the bimetal elementis secured are adaptedto be slidably received in the recesses provided therefor by slidingthese elements sidewise through the open side of the housing section 3|into the recesses. The stationary core of the electromagnet and thebracket of the bimetal element are maintained in proper position by theengaging and supporting surface provided therefor in thehousing section3|. The stationary core I51 of the electromagnet is prevented from beingmoved in a vertical direction by the surfaces I3I and I31 and by theengagement of the pivot pin I in the bearing recesses I35 and I91.Counterclockwise or clockwise twisting or turning of the magnet core isprevented by reason of the engagement of the surfaces I33 and I35 withone-leg of the magnet core and by the surfaces I9I and I89 which engagethe other leg of the magnet core. Similarly, the bracket I15 of thebimetal element is prevented from being moved vertically or from beingtwisted in a clockwise or counterclockwise direction by reason of theengagement thereof in the notch MI and in the recess 205. The lowersurface of the projection I93 also prevents vertical or twistingmovement of the bimetal bracket. It will also be noted that the reactionforces on the various elements of the circuit breaker mechanism and tripdevice cause them to naturally seat against the fixed surfaces providedtherefor in the housing, thereby providing substantially constantperformance irrespective of the degree of tightness or looseness of fitof the elements in the housing. For example, the reaction on the latchlever I5I caused by the overcenter spring II1 causes the ends of thepivot pin I35 to always engage the front side of the bearing recessesI95 and I31 and also causes the magnet core I51 to more firmly seatagainst the surfaces I9I and I35. Similarly, the reaction force on thebimetal element I55 causes its bracket I15 to seat against the fixedsurface of the lower wall of the slot 2M and against the surface 201 ofthe projection I". It should also be noted that the reaction force ofthe spring II! is transmitted through switch arm 2I and supportingmember H3 to the pivot pin I29 and thereby biases it to bear against theright-hand side (when viewed as in Fig. 1) of the recesses I3I and I33.The fact that the recesses I3I and I33 and the holes of the member II3are cylindrical results in the member II! being held by the bias thereonin the same position vertically. This construction together with thesimilar construction and bias on pivot pin I65 give a constant amount ofoverlap between the latch elements Ill and I61. This gives the advantagethat the calibration of the breaker remains constant even though theremay be looseness in the mounting of the parts and wear of the bearingsurfaces.

All of the aforementioned parts of the circuit breaker, including theterminals, the operating means, and the trip device, are fitted into therecesses provided therefor through the open side of the housing sectionSi by sliding the elements sidewise into their recesses, and all of theparts are retained in mounted position when the housing sections 3| and33 are assembled without any of the parts of the circuit breaker beingpositively fastened to either of the housing sections. To remove thecircuit breaker parts it is only necessary to remove the cover section33 of the housing and slide the parts sidewise out of the housingsection 3i through the open side thereof.

The ,manual operation of the circuit breaker has previously beendescribed. The automatic operation of the breaker onoverload is brieflyas follows: As the current of the circuit increases above the normalrated current, the bimetallic element I55 is heated thereby andgradually decreases its restraining force which opposes release of thelatch lever II. At the same time the pull or unlatching force of theelectromagnet I53 increases with the increase in current. The latchlever I5I is moved to the unlatched position as soon as the combinedforce of the electromagnet I53 and spring IE8 is sufllcient to overcomethe resilient opposing force of the bimetal element I55. The bimetalelement I55 introduces a time delay action between the occurrence of theoverload and the tripping or release of the circuit breaker mechanism upto a predetermined current value, for example, about 1000% of the ratedcurrent, Upon overload currents in excess of this predeterminedmagnitude the electromagnet I53 exerts sufilcient pull to effectsubstantially instantaneous tripping of the circuit breaker irrespectiveof the opposing force of the bimetal element I55, that is, even thoughthe bimetal element may not have been heated a substantial amount. Thetime delay action introduced by the bimetal element in the range ofoverloads below the predetermined instantaneous tripping value variesinversely with the magnitude of the current, the time delay beinggreatest for light overloads and gradually decreasing as the value ofthe current increases. The arrangement of the parts of the trip deviceare such that the device operates to trip or release the breakermechanism faster, that is, with shorter time delay in theintermediate'range of overload currents than conventional circuitbreakers havin a bimetal trip element and an electromagnet which actindependently to trip the breaker. This result is obtained principallyby reason of the fact that the electromagnet I exerts an unlatchingforce at all times when it is energized which force increases with theincrease in current while the bimetal element merely resiliently opposesunlatching with a force which decreases as the element is heated by thecurrent. The unlatching force of the electromagnet becomes appreciablein the intermediate range of overload currents. As a result less heatingof the bimetal element is required to cause unlatching than if the forceof the electromagnet were not present. The provision of the doublearmature comprising the two sections I51 and Ill separated by the lowresistance conducting material of the latch lever I5I tends to increasethe time delay action to a certain extent in the case of heavy overloadsless than the predetermined magnitude, that is, less than short circuitmagnitude by reason of the fact that the magnetic flux in passingthrough the upper armature traverses the low resistance conductingmaterial of the latch lever III and thus sets up eddy currents whichtend to reduce the magnetic flux and delay the time of its maximumvalue. The pulls of the two armatures are, therefore, out of phase. Thishas the effect of delaying the time of maximum pull and reducing thevalue of maximum pull. There will be little, if any, eilect of the eddycurrents for lower magnitude overloads until the iron of the lowerarmature I59 becomes saturated. From this point on the upper armatureI5I comes into action more strongly but somewhat held back by thecounter flux produced by the eddy currents. This construction allowsheavy overloads to exist for a slightly longer time without tripping thebreaker than in the case of a single armature. On short circuit,however, both armatures become saturated and the eddy currents areineffective to delay tripping of the breaker. This feature is ofparticular advantage in connection with the lighting of tungsten lamploads as it enables the lighting of a greater number of tungsten lampswithouthtripping the breaker on the initial current rus An importantfeature of the present invention is the provision of a circuit breakerconstruction in which several different types of trip devices may besubstituted for controlling the same mechanism, and can be removablymounted in the same housing. For this purpose the housing of the circuitbreaker is provided with recesses and surfaces such as to receive andsupport either a combined magnetically and thermally responsive tripdevice such as shown in Fig. 1 and described in connection therewith, ora pure thermally responsive trip device as shown in Fig. 8, or amagnetically responsive trip device as shown in Fig. 9. This is aparticularly desirable feature since it enables a complete line ofcircuit breakers to be manufactured using a single molded housingconstruction and the same type of mechanism, thereby materially reducingthe cost of the circuit breakers and simplifying the stocking of parts.

Fig. 8 shows the circuit breaker equipped with a thermally responsivetrip device comprising a bimetal element 2| I, the free end of whichforms a latch for engaging the latch element III of the releasablesupport lever III. The housing construction, the upper terminal, thecontact means, the operating means and the arc extinguishing structureare all of identical construction to that shown in Figs. 1-6 anddescribed in connection therewith, and the same reference characters areused to designate the identical 13 parts. The thermally responsivebimetal trip element 2 comprises a flat strip of bimetallic materialbent in a U-shape and is secured at its lower end to the reversely bentend of the terminal strip 2I3. The terminal strip 2I3 has a rightangledbend therein and the strip flts snugly in the slot 9| and in a portionof the elongated slot 2M formed in the housing section 3|, as shown inFig. 8. The terminal end of the terminal strip 2 I3 is provided with alug (not shown) on one side thereof which fits snugly in the rectangularrecess 81 of the housing section 3i in the same manner as the lug 85 ofthe terminal 29 shown in Fig. 4. The terminal 3 and the bimetal element2| I carried thereby are fitted into the housing section 8| by slidingthe same edgewise into the slots 9| and MI in the position shown in Fig.8 and are securely retained in mounted positions when the housingsections 3i and 33 are assembled. The free end of the bimetal elementIII is connected by a flexible shunt conductor II! to the releasablepivoted supporting lever I I3 and is thereby electrically connected inseries with the contacts of the breaker so as to be traversed by thecurrent flowing through the circuit controlled by the breaker. Uponoverload of the circuit, the bimetal element ZII is heated by theoverload current and upon attaining a predetermined temperature the freeend thereof deflects downwardly away from the circuit breaker mechanismand effects release of the pivoted supporting lever I33, thereby causingautomatic opening of the circuit breaker contacts. After the bimetal hascooled following interruption of the circuit, the free end thereofreturns to the normal position shown in Fig. 8 and the breaker may bereset manually by moving the operating handle downwardly to the openposition.

An adjusting screw 2 I6 is threaded in an opening provided therefor inthe terminal 2I3 and the point of the screw engages the reversely bentend of the terminal as shown in Fig. 8. The screw 2 I8 serves as a meansfor calibrating and adjusting the trip characteristic of the breaker bychanging the amount of overlap of the latch end of the bimetal elementwith respect to the latch element I2I of the breaker mechanism. When thescrew is turned clockwise the reversely bent end of the terminal i movedupwardly, increasing the amount of overlap of the latch, and converselywhen the screw is turned counterclockwise, the reversely bent end of theterminal .moves downwardly due to its resiliency and thereby decreasesthe amount of latch overlap. The screw 2H5 may be adjusted from outsidethe housing through the opening I12.

The circuit breaker as equipped with a magnetically responsive tripresponsive device is shown in Fig. 9. The magnetically responsive tripdevice is identical in construction to the trip device shown in Figs. 1through 6, except that the bimetal element is omitted, and a compressionspring 2II is substituted in place of the tension spring I68 used in theembodiment of the invention shown in Figs. 1 through 6. Since themagnetically responsive device is identical in construction to the tripdevice shown and described in connection with the original embodimentwith the exceptions noted above, the same reference characters have beenused to designate the corresponding parts and it is not believednecessary to again describe the construction. The magneticallyresponsive trip device is removably fittedin the housing in the samemanner as the trip device of the original embodiment, fltting into 14the same recesses and engaging the same surfaces.

The bracket I1! to which the upper end of the energizing winding I83 ofthe electromagnet is connected is in turn electrically connected to thereleasable support member I I3 by a flexible shunt conductor 2I8,thereby connecting the winding in series with the contacts of thebreaker. The latch lever IBI is in this instance biased to latchingposition by the compression spring 2", and the strength of the spring isadjusted by the screw I13 so that the breaker will be automaticallytripped by the electromagnet whenever the current exceeds thepredetermined selected value.

A modification of the invention is shown in Fig. 7. This modification ofthe invention is identical in construction and operation to theembodiment of the invention shown in Figs. 1 through 8 and described inconnection therewith except that a resilient element in the form of aspring strip II! of predetermined strength is interposed between thefree end of the bimetal element It! and the end of the latch lever Iii.The spring strip 2 I9 is fastened to the lower side of the free end ofthe bimetal element I55 by means of a rivet HI and the inner end of thestrip engages the insulating button I" of the latch lever IUI. When thebimetal element I55 is in the normal position shown in Fig. 7, thespring strip 2 I 9 carried thereby provides a substantially constantforce opposing unlatched movement of the latch lever IEI, and the springstrip and bimetal element normally maintain the latch lever in latchingposition. As the current of the circuit increases beyond the normalrated current, the bimetallic element I55 is heated thereby and the freeend thereof gradually deflects downwardly, decreasing the restrainingforce opposing unlatching until the breaker is finally tripped by theunlatching force of the electromagnet I53 and spring I68. The latchlever Iii is moved to the unlatched position as soon as the combinedforce of the electromagnet I53 and spring I" is sufficient to overcomethe opposing force of the leaf spring 2I9, or as soon as the bimetalelement I55 has deflected a sufficient amount to permit unlatching. Uponthe occurrence of overload currents in excess of a predetermined value,for example, about 1000% of the rated current, the pull of theelectromagnet is sufficient to deflect the leaf spring H9 and cause therelease of the latch lever Iii even though the bimetal element I55 maynot have been heated a substantial amount. It will thus be seen that theprovision of the resilient element or leaf spring 2l9 provides apredetermined and substantially constant force opposing unlatching ortripping of the breaker which is independent of the thickness orstiffness of the bimetal element I55. This enables bimetal elements ofdifferent thickness and stiffness to be substituted without changing theinstantaneous trip setting of the breaker. In other words the breakerwill be tripped instantaneously whenever the current exceeds apredetermined high value, i'or example, 1000% of the rated currentirrespective of what the thickness or stiffness of the bimetal elementmay be.

While the invention has been disclosed in accordance with the provisionof the patent statutes, it is to be understood that various changes inthe structural details thereof may be made without departing from someof the essential features of the invention. It is desired, therefore.that the language of the appended claims be given the broadestreasonable interpretation permissible in the light of the prior art.

I claim as my invention:

1. A circuit breaker comprising, in combination, relatively movablecontacts, operating means therefor operable to open and to close saidcontacts, a trip device including a bimetal element having a stationaryend and a movable end' operable to cause opening of said contacts,terminals for connecting the breaker in an electrical circuit, one ofsaid terminals being connected to the stationary end of the bimetalelement by a conductor permitting some relative movement between theterminal and bimetal element, an insulating housing for theaforementioned parts comprising two separable sections having a jointbetween them, said housing serving as the frame for the breaker andhaving recesses and projections for supporting said parts without any ofsaid parts being positively fastened to said housing, said parts beingremovably mounted through the open side of one of said sections at thejoint when the sections are separated and being retained in mountedposition when the housing sections are assembled and said stationary endof the bimetal element being biased against the housing in a directionto take up any looseness in its mounting which would affect thecalibration of the breaker.

2. A circuit breaker comprising, in combination, an open-sided casing ofinsulating material having covering means for the open side, astationary contact, a cooperating movable switch member, operating meansfor moving said switch member to op n and to closed circuit position, atrip device including a bimetal element having a stationary end and amovable end operable to cause movement of said switch member to opencircuit position independently of the position of said operating means,terminals for connecting the breaker in an electrical circuit, one ofsaid terminals being connected to the stationary end of the bimetalelement by a conductor permitting some relative movement between theterminal and bimetal element, said casing having means for receiving andsupporting all of the abovementioned parts whereby all of said parts areremovably mounted in said casing through the open side and are retainedin mounted position without any fastening devices when the cover is inmounted position on said casing.

3. A circuit breaker comprising, in combination, relatively movablecontacts, operating means manually operable to open and to close saidcontacts, a trip device including a bimetal element having a stationaryend and a movable end operable in response to predetermined conditionsto cause automatic opening of said contacts, terminals for connectingthe breaker in an electrical circuit, one of said terminals beingconnected to the stationary end of the bimetal element by a conductorpermitting some relative movement between the terminal and bimetalelement, aninsulating housing for the aforementioned parts comprisingtwo separable members having a joint therebetween, said housing servingas the frame for the breaker and having means of the insulating materialof said housing for mounting and directly supporting the stationary endof said bimetal elements and the terminal connected thereto withouteither-of said last mentioned parts being positively fastened to saidhousing and said stationary end of the bimetal element being biasedagainst the housing in a direction to take up any looseness in itsmounting which would affect the calibration of the breaker.

4. A circuit interrupter comprising circuit making and breakingmechanism including a bimetal element having a stationary end and amovable end, terminals for connecting the interrupter in an electricalcircuit, one of said terminals being connected to the stationary end ofthe bimetal element by a conductor permitting some relative movementbetween the terminal and bimetal element, an insulating housing for theinterrupter comprising two separable members having a Joint betweenthem, at least one of said housing members serving as the frame for thecircuit making and breaking mechanism and having means for removablymounting and supporting said mechanism without any part of saidmechanism being positively fastened to said housing, said housing memberalso having recesses and surfaces for engaging and fixedly supportingsaid terminals without said terminals being positively fastened to saidhousing, said mechanism and terminals being removably mounted throughthe open side of said housing member at the joint when said housingmembers are separated and being securely retained in mounted positionwhen said housing members are assembled.

5. A circuit breaker comprising circuit making and breaking mechanism, athermally responsive element of bimetallic material operable in responseto predetermined conditions to cause a circuit opening operation of saidmechanism, an insulating housing for the breaker comprising twoseparable members having a Joint between them, at least one of saidhousing members forming the frame of the breaker and having means forsupporting said mechanism without any part of said mechanism beingpositively fastened to said housing, said housing also having one ormore recesses and surfaces for receiving and fixedly supporting one endof said bimetal element against movement in all directions exceptoutwardly through the open side, and said housing member slidablyreceiving said mechanism and bimetal element through its open side atthe Joint so that when the housing members are assembled the said partsare securely retained in mounted position without being positivelyfastened to said housing.

6. A circuit breaker comprising circuit making and breaking mechanism, athermally responsive element of bimetallic material operable in responseto predetermined conditions to cause circuit opening operation of saidmechanism, an insulating housing for the breaker comprising twoseparable members having a joint between them, said housing serving asthe frame for the breaker and having means for mounting said mechanismwithout any part of said mechanism being positively fastened to saidhousing and having means for fixedly supporting one end of said bimetalelement without said element being positively fastened to said housing,said mechanism and said bimetal element being removably mounted in saidhousing through the open side of one of said housing members at thejoint when the members are separated and being retained in mountedposition when the housing members are assembled.

'I. A circuit breaker comprising, in combination, contact means andoperating means or opening and closing said contact means, anelectromagnet energized in response to the current of the circuitoperable in response to predetermined conditions to cause automaticopening of said contact means, an insulating housing for the breakercomprising two separable insulating members having a Joint between them,said said contact means and operating means and also having recesses andsurfaces for engaging and supporting an element of said electromagnet,said contact means and operating means and said electromagnet beingremovably mounted in said housing through the open side of one of saidhousing members at the joint when said housing members are separated andbeing 58-- curely retained in mounted position when said housing membersare assembled without any of said parts being positively fastened tosaid housing members.

8. A circuit breaker comprising, in combina-- tion, a stationarycontact, a cooperating movable switch member, operating means for movingthe switch member to open and to closed circuit position, a trip devicecomprising an electromagnet energized in response to the current of thecircult operable in response to predetermined conditions to causemovement of the switch member to open circuit position, terminals forconnecting the breaker in an electrical circuit, an insulating housingfor the breaker comprising two separable members having a Joint betweenthem, said housing serving as the sole frame for the breaker and beingformed to provide recesses and surfaces for receiving and supporting allof the aforementioned parts without any of said parts being positivelyfastened to said housing members, said aforementioned parts beingremovably mounted through the open side at the Joint of one of saidhousing members when the housing members are separated and beingretained in mounted position when the housing members are assembled.

9. A circuit breaker comprising, in combination, an open-sided casing ofinsulating material, a stationary contact, a cooperating movablecontact, operating means for opening and closing said contacts, a tripdevice comprising an electromagnet and a bimetal element energized inresponse to the current of the circuit and operable in response topredetermined conditions to cause automatic opening of the contacts,terminals for connecting the breaker in an electrical circuit, saidcasing being formed to provide recesses and surfaces for removablyreceiving the aforementioned parts through the open side and forsupporting said parts, a second casing member for completing the casingand holding the above-mentioned parts in mounted position whereby saidparts are retained in mounted position without any of said parts beingpositively fastened to said casing members.

10. A circuit breaker comprising, in combination, contact means,operating means for opening and closing said contact means including aspring biased member releasable to cause automatic opening of saidcontact means, a, trip device comprising a current responsive bimetalelement normally restraining said spring biased member and operable inresponse to predetermined conditions to cause release of said member,thereby effecting automatic opening of said contacts, an insulatinghousing for the breaker comprising two separable sections having a jointbetween them, said housing serving as the frame of the breaker and beingformed to provide recesses and surfaces for receiving and supportingsaid contact means and operating means without said parts beingpositively fastened to said housing, and said housing also havingadditional recesses and surfaces for engaging and fixedly supporting oneend of said bimetal element to support the bimetal element in properposition relative to said releasable member without said bimetal elementbeing positively fastened to said housing, said contact means and saidoperating means and said bimetal element being removably mounted in saidhousing through the open side of one of said housing members at thejoint when said housing members are separated and being retained inmounted position when said housing membersare assembled, said supportingsurfaces being disposed so that the reaction forces on said parts causethem to seat against said surfaces in such a, manner that the accuracyof operation of the breaker is substantially unaffected by the degree oflooseness of fit of said parts in said housing.

11; A circuit breaker comprising, in combination, contact means,operating means for opening and closing said contact means including apivoted spring biased member releasable to cause automatic opening ofsaid contact means, a pivoted latch for normally restraining saidreleasable member, electro-responsive means operable in response topredetermined conditions to cause release of said latch, an insulatingcasing for the breaker comprising two separable sections having a jointbetween them, said housing forming the sole frame for the breaker partsand having bearing recesses for the pivots of said releasable member andsaid latch and having additional recesses and surfaces for supportingthe other aforementioned parts without any of said parts beingpositively fastened to said housing, said parts being removably mountedin said housing through the open side of one of said housing sectionswhen the housing sections are separated and being retained in mountedposition when the housing sections are assembled, said parts and thesurfaces against which they bear being disposed so that the reaction onsaid parts cause them to naturally seat against the surfaces in such amanner that the accuracy of operation of the breaker is substantiallyunaffected by the degree of looseness of fit of said parts in saidhousing.

12. A circuit breaker comprising relatively movable contacts, operatingmeans for opening and closing said contacts, an electromagnet energizedin response to the current of the circuit and operable in response topredetermined conditions to cause automatic opening of said contacts, aninsulating housing for the breaker comprising two separable membershaving a joint between them, at least one of said housing membersserving as the frame of the breaker and having means for receiving andfor supporting said contacts and operating means without beingpositively fastened thereto and having recesses and surfaces forreceiving and supporting an element of said electromagnet without saidelectromagnet being positively fastened to said housing.

13. A circuit breaker comprising, in combination, contact means,operating means therefor including a manually operable operating member,a thermally responsive bimetal element fixedly mounted .at one end andoperable in response to predeterminedoverload condition to causeautomatic opening of the contact means, terminals for connecting thebreaker in an electrical circuit, an insulating housing for enclosingall of the aforementioned parts other than the operating end of themanually operable member and the terminal ends of said terminals andcomprising two separable members having a joint between them gene yparallel to the plane of movement of said contact means, Sai housingserving as the sole frame for the breaker and having recesses andsurfaces for supp ing all of the above-mentioned parts in operativeposition without any of said parts being positively fastened to saidhousing, said parts being removably mounted through the open side of oneof said housing members at the joint when the housing members areseparated and being retained in mounted position therewithin when thehousing members are assembled.

14. A circuit breaker comprising, in combination, an open sided casing,contact means, operating means therefor including a manually operableoperating member for manually operating said contact means, anelectromagnet energized by the current of the circuit operable inresponse to predetermined conditions to cause automatic opening of saidcontact means, terminals for connecting the breaker in an electricalcircuit, said casing serving as the frame for the breaker and havingrecesses and surfaces for slidably receiving the aforementioned partsthrough the open side and for supporting the aforementioned parts, asecond casing member for completing the casing and holding all of theabove-mentioned parts in mounted position therewithin without any ofsaid parts being positively fastened to said casing members.

15. A circuit breaker comprising, in combination, an open sided casingof insulating material, a stationary contact, a cooperating movableswitch member, operating means for said switch member including amanually operable operating member, an actuating spring connecting saidoperating member and said switch member, a pivoted member releasable tocause movement of said switch member to open circuit position, and atrip device mounted separately from said switch member and releasablemember normally restraining said releasable member and operable inresponse to predetermined condition to effect release of said releasablemember, said casing having recesses and surfaces for receiving andsupporting the aforementioned parts including a surface forming onebearing for said operating member on one side of said spring, a secondcasing member removably mounted on the open side of said casing forcompleting the casing, said second casing member having a bearingsurface forming a second bearing for said operating member on the sideof the spring opposite the first bearing, all of said parts beingremovably mounted through the open side of said casing and beingretained in mounted position therewithin by said second casing memberwithout any of said parts being positively fastened to said casingmembers.

16. A circuit breaker comprising, in combination, an open-sided casingof insulating material, a stationary contact, a cooperating movableswitch member, operating means for moving the switch member to open andto closed circuit position comprising a manually operable operatinglever, an actuating spring connecting said operating lever and saidswitch member, trip means operable in response to predeterminedconditions to cause movement of said switch member to open circuitposition irrespective of the position of said operating lever, saidcasing serving as the frame for the breaker and having recesses andsurfaces for supporting the aforementioned parts without beingpositively fastened thereto, one of said surfaces being formed on thewall of said casing opposite the open side and forming one pivot bearingfor engaging and supporting the lever at one side of said actuatingspring, said operating lever having a lateral projection adjacent itsoperating end carrying a rotatable roller on the other side of saidactuating spring, a second casing member removably mounted on the openside of said casing for completing the casing and retaining theaforementioned parts therewithin, said second casing member having anarcuate bearing surface engaged by said roller and along which saidroller is movable to form a second bearing for the operating lever.

17. A circuit breaker comprising an open-sided casing of insulatingmaterial, contact means, operating means for opening and closing saidcontact means, said casing serving as the frame for the breaker andhaving recesses and surfaces for receiving and supporting said parts andhaving additional recesses and surfaces disposed for receiving andsupporting a combined magnetically and thermally responsive trip devicecomprising an electromagnet and a bimetal element, and for receiving andsupporting a thermally responsive trip device comprising a bimetal tripelement when said magnetically and thermally responsive trip device isremoved, and for receiving and supporting a magnetically responsive tripdevice comprising an electromagnet in place of either of the other tripdevices, a closure member removably mounted on the open side of saidcasing for completing the casing and for retaining said contact meansand operating means and whichever trip device is inserted all in mountedposition in said casing, said parts being removably mounted in thecasing through the open side and retained in mounted position by theclosure member without any of said parts being positively fastened tosaid casing and closure member.

18. A manually and automatically operable circuit breaker comprising anopen-sided casing of insulating material, contact means, operating meansfor opening and closing said contact means, said casing serving as theframe for the breaker and having recesses and surfaces for receiving andsupporting said contact means and operating means and having additionalrecesses and surfaces for receiving and supporting a combinedmagnetically and thermally responsive trip device comprising anelectromagnet and a current responsive bimetal element for tripping saidbreaker in response to predetermined conditions, and for receiving athermally responsive trip device comprising a current responsive bimetaltrip element when said other trip device is removed, a closure memberremovably mounted on the open side of said casing for completing thecasing and for retaining said contact means and said operating means andwhichever trip device is inserted all in mounted position in said casingwithout any of said parts being positively fastened to said casing orclosure member.

19. A manually and automatically operable circuit breaker comprising anopen-sided casing of insulating material, contact means, operating meansfor opening and closing said contact means, said casing serving as theframe for the breaker and having recesses and surfaces for receiving andsupporting said contact means and operating means and having additionalrecesses for receiving and supporting a magnetically responsive tripdevice comprising an electromagnet for tripping said breaker in responseto predetermined conditions, and for receiving and supporting athermally responsive trip device comprising a current responsive bimetaltrip element when said magnetically responsive trip device is removed, asecond casing member removably mounted on the open side of the casingfor completing the casing and retaining said contact means and operatingmeans and whichever trip device is inserted all in mounted positionwithin said casing, said parts being removably mounted through the openside of the casing and retained in mounted position without any of saidparts being positively fastened to said casing members.

20. A circuit breaker comprising, in combina tion, contact means,operating means for openlng and closing said contact means including apivoted spring biased member releasable to cause automatic openingofsaid contact means,

an electroresponsive latch operable in response to predeterminedconditions to cause release of said releasable member, an insulatingcasing for the breaker comprising two separable sections having a jointbetween them, said housing forming a frame and having separate bearingsurfaces for the pivot of said releasable member and for said latchwithout either said releasable member or said latch being positivelyfastenedto said housing, said releasable member and said latch beingremovably mounted in said housing through the open side of one of saidhousing sections when the housing sections are separated and beingretained in mounted position when the housing sections are assembled,said releasable member and said latch being biased against theirbearings and said surfaces being shaped so that the bias on said partscause them to naturally seat in a certain position. against theirbearing surfaces in such a manner that there is a fixed overlap betweensaid releasable member and said latch under any given electroresponsivecondi tion and the accuracy of operation of the breaker is substantiallyunaffected by the degree of looseness of fit of said parts in saidhousing.

21. A circuit breaker comprising contact means, operating means foropening and closing said contact means including a pivoted spring biasedmember releasable to cause automatic opening of said contact means, anelectroresponsive latch engageable with said releasable member andpivoted about an axis parallel to the pivot axis of the releasablemember, said latch being operable in response to predeterminedconditions to release said member, an insulating casing for the breakercomprising two separable sections having a joint between them, saidcasing forming a frame and having separate generally cylindrical bearingsurfaces for the pivots of said releasable member and latch withouteither said releasable member or said latch being positively fastened tosaid casing, said releasable member and said latch being removablymounted in'said casing through the open side of one of said sectionswhen the sections are separated and being retained in mounted positionwhen the sections are assembled, and said releasable member and latch inthe latched position being biased against their bearings so that thepressure on the pivot bearing of the releasable member is in the samedirection and parallel to the pressure on the pivot bearing of the latchthereby maintaining a fixed overlap between the latch and the releasablemember under any given electroresponsive condition and maintaining theaccuracy of operation of the breaker irrespective of the looseness offit of said parts in said casing.

22. A circuit interrupter comprising contact means, operating means foropening and closing said contact means including a manually operableoperating member having a handle portion, an insulating housing forenclosing the parts of the circuit interrupter except the handle portionof said operating member, said housing comprising two separable sectionshaving a joint therebetween, portions of said housing sectionsoverlapping one another in spaced relation to provide a slot throughwhich a portion of said operating member extends and said last mentionedportion of the operating member being bent to extend parallel to andbetween the opposed surfaces of the overlapped portions of said housingsections.

23. A circuit interrupter comprising contact means, operating means foropening and closing said contact means including a manually operableoperating member having a handle portion, an insulating housing forenclosing the parts of the circuit interrupter except the handle portionof said operating member, said housing comprising two separable sectionshaving a joint therebetween extending in a direction generally parallelto the plane of movement of said handle portion, portions of saidhousing sections overlapping one another in spaced relation to provide aslot extending at substantially a right angle to said plane of movementand through which a portion of said operating member extends and saidlast mentioned portion of the operating member extending substantiallyparallel to and between the opposed surfaces of the overlapped portionsof said housing" sections.

24. A circuit breaker comprising, in combination, contact means,operating means for said contact means including a spring biased memberreleasable to cause automatic opening of said contact means, a magneticpole piece, an armature pivoted thereon and having a latch portionnormally in latching engagement with said spring biased member butreleasing it upon the occurrence of an abnormal condition, a housing forthe circuit breaker including a housing section of in sulating materialhaving recesses for supporting said parts without any of said partsbeing fastened to said housing, and the pivot of said armature extendinginto said pole piece and into the insulating material of the housingsection for accurately positioning said latch portion in position toengage said spring biased member.

25. A circuit breaker comprising, in combination, contact means,operating means for said contact means including a pivoted spring biasedmember releasable to cause automatic opening of said contact means, amagnetic pole piece, an armature pivoted thereon and having a latchportion normally in latching engagement with said spring biased memberbut releasing it upon the occurrence of an abnormal condition, a housingfor the circuit breaker including a housing section of insulatingmaterial, the pivot of said spring biased member engaging a bearingsurface on said insulating material and the pivot of said armature onsaid pole piece also engaging a hearing surface on said insulatingmaterial, and each of said pivots being biased against its bearingsurface and said surfaces being shaped so that the bias on the pivotscauses them to seat in a certain position and provide a definitelatching relation between said spring biased member and the latchportion of the armature.

' OLIVER S. JENNINGS.

(References on following page) The following references are of record inthe REFERENCES CITED file of this patent:

UNITED STATES PATENTS Number Name Date Dorfman Aug. 11, 1936 Number

